Conventional snow plows comprise a vehicle, such as a truck, a moldboard laterally extending in front of the truck and adapted to contact and displace snow, ice, or another form of frozen water, and a frame interconnecting the moldboard to the vehicle.
When a snow plow traverses a ground terrain such as a paved road, a parking lot, or an airport run way, several forces act on the snow plow, especially the moldboard, to cause severe vibrations. Vibrations might be caused, for example, by encountering snow of a different depth or consistency, by encountering bumps or other curvatures in the ground terrain, by turning or acceleration and deceleration of the vehicle, or by encountering obstacles in the path of the snow plow.
The vibration forces are typically transmitted from the moldboard, through the frame, and to the vehicle. At each point of transmission, the vibrations may produce stress on the structure such that it cracks, is loosened, or is otherwise disabled and also cause discomfort to the operator of the vehicle from being jostled. The vibrations may require frequent inspection of the moldboard and the frame and the replacement of various components thereof, and may even result in the disabling of the snow plow at critical times and locations either during use or when needed for use.
To date, attempts to minimize the effects of vibrations in snow plows have included designing the moldboard and the frame of stronger, typically heavier and more expensive, materials and components and providing springs, pneumatic or hydraulic shock absorbers, and elastomeric materials that passively, resiliently absorb the vibration to a certain degree, and then return to a normal state.
The present invention relates to a system and method of actively inducing vibrations in a snow plow that tend to substantially neutralize, negate, or cancel vibrations resulting from vibrations of the snow plow over a ground terrain to displace forms of frozen water.
Vibrations are essentially a pressure wave consisting of compression and rarefaction through a medium, i.e., a gas, a liquid, or a solid. When a pressure wave creates vibrations of certain frequencies within the audible range of the human ear, the vibrations are usually referred to as sound. To further distinguish audible sound, when the pressure waves are regularly recurring or periodic, they are sometimes what is referred to as a musical sound, and otherwise, just a sound or noise.
In one aspect, the present invention preferably senses when and where a compression or rarefraction occurs and when and where that same compression or rarefraction will occur in other places in the snow plow due to vibrations caused by use of the snow plow. The invention then preferably, typically induces or imparts into the snow plow a rarefaction where the compression is occurring and a compression where the rarefaction is occurring, thus tending to cancel the pressure wave. This process may also be known as inducing or imparting a destructive interference into the snow plow.
A simple illustration of destructive interference is depicted in FIG. 1. The dashed line 10 represents a regular, periodic pressure wave in which the Y axis indicates the amplitude of the pressure wave, and the X axis indicates the time or travel of the pressure wave. When the dashed line 10 is above the X axis, the wave is in a state of compression, and when the dashed line is below the X axis, the wave is in a state of rarefaction. The dotted line 12 indicates a pressure wave having the same periodic frequency, but one-half of a cycle out of phase. The dotted line 12 is thus also referred to as an anti-phase or an opposite phase pressure wave. In the example shown in FIG. 1, the dotted line 12 represents an anti-phase or an opposite phase pressure wave in which the amplitude of the wave is exactly equal to and opposite to the amplitude of the pressure wave shown by the dashed line 10. When a vibration such as that shown by the dashed line 10 travels through a medium such as a snow plow moldboard and frame, an opposite phase vibration such as that shown by the dotted line, may be induced and imparted into the moldboard or frame with a result that the vibrations cancel each other and there is no vibration, as indicated by the solid line 14 extending along the X axis.
The example illustrated in FIG. 1 is very simplistic. Most pressure waves are non-periodic, and are very erratic in both amplitude and frequency. Further, the illustration in FIG. 1 is idealized because it presumes that the vibration of the pressure wave depicted by the dashed line 10 can be instantaneously determined and that an opposite phase pressure wave might be instantaneously, exactly generated to cancel or negate the effect of the original pressure wave depicted by the dashed line 10.
Further complications arise in generating an opposite phase pressure wave because the location of detecting the vibration may be different from, and separated from, the location where an opposite phase vibration is imparted into the snow plow. Since pressure waves, such as sound, do not travel through media instantaneously, there is a time lag between when the vibration is detected and when the same vibration reaches the point where the opposite phase vibration is to be imparted. For example, a sound wave normally propagates or travels through the atmosphere at about 1,100 feet per second, travels faster through liquids, and even faster through solids. Thus, if a vibration is detected at one location in the snow plow and an opposite phase vibration is imparted at a different location in the snow plow even a few feet away, there will be a few milliseconds difference between the time of detection and the time when the vibration reaches the point where the opposite phase vibration is to be imparted.